Mac OS X is 64-bit only since 10.7 (Lion), which has reached End-Of-Life in October 2014.
Therefore it no longer makes sense to support exporting 32-bit binaries for Mac OS X,
and we can now default to 64-bit instead of bigger "fat" binaries.
Using `misc/scripts/fix_headers.py` on all Godot files.
Some missing header guards were added, and the header inclusion order
was fixed in the Bullet module.